Slaughter and May and Sullivan & Cromwell have assisted Standard Chartered Bank to come to a final settlement with US authorities over allegations that it had breached US sanctions policy.

The firms have negotiated a deferred prosecution agreement (DPA) with the US Department of Justice, the New York County District Attorney’s Office, the Federal Reserve Bank of New York, and Office of Foreign Assets Control, which includes a total penalty of $327m (£203m).

The Slaughter and May team was led by corporate partner Nigel Boardman and dispute resolution partner Richard Swallow, who were supported by dispute resolution senior associate Stephanie Stapley.

The Sullivan & Cromwell team was led by high profile corporate and financing partner and senior chairman Rodgin Cohen and dispute resolution partners Samuel Seymour and Nic Bourtin.

The Standard Chartered legal team was led by group head of legal James Ellington.

Both firms also acted on the UK bank’s agreement in August with the New York State Department of Financial Services in relation to the same sanctions investigation – for which Standard Chartered agreed to pay a civil money penalty of $340m (8 August 2012).

The bank issued a statement saying the settlements were the result of an “extensive internal investigation” which led Standard Chartered to “voluntarily report” to US authorities and three years of negotiations with regulators and prosecutors in the States.

No further action will be taken against the bank if it complies with the conditions of the DPA.

The bank confirmed: “The payment is for past violations of sanctions laws and the lack of transparency in connection with certain former payment practices which were terminated in 2007. In the more than five years since the events giving rise to today’s settlements, the bank has completed a comprehensive review and upgrade of its compliance systems and procedures.”

The OFAC also found that there had been transactions on behalf of entities in Burma, Sudan and Libya that breached sanctions laws.

Assistant US attorney general Lanny Breuer said: “For years, Standard Chartered Bank deliberately violated US laws governing transactions involving Sudan, Iran and other countries subject to US sanctions. The United States expects a minimum standard of behaviour from all financial institutions that enjoy the benefits of the US financial system. Standard Chartered’s conduct was flagrant and unacceptable.”